The present invention relates to an optical disk apparatus that reproduces different kinds of disks, such as a compact disk and a digital video disk.
There is an optical disk apparatus in which a light beam emitted from a laser is focused on a rotating disk to reproduce signals recorded in the disk.
FIG. 25 is an enlarged view of a part of a typical compact disk (hereinafter referred to as CD). In the figure, reference numeral 1 designates a base substrate of the CD, numeral 2 designates an information surface, and numeral 3 designates a series of pits on the information surface. These pits 3 provide a spiral track. The pitch of the spiral track is 1.6 xcexcm. Aluminum is vapor-deposited on the information surface 2 as a reflecting film. The rear surface of the disk, opposite the information surface 2, is irradiated with a light beam. When information recorded on the track is reproduced, focusing is performed so that a focal point of the light beam is always positioned on the information surface 2 where the Al reflecting film is present, and tracking is performed so that the focal point of the light beam is positioned on the track. The diameter of the disk is about 120 mm, and the thickness of the base substrate 1 is 1.2 mm. The wavelength of the light beam is 780 nm.
In recent years, disks with high recording density, for example, a digital video disk (hereinafter referred to as DVD) in which digital image data are recorded, have been proposed. Hereinafter, a DVD will be described as an example of a high recording density disk. However, the present invention is not restricted to a DVD.
The recording density of the DVD is about five times as high as that of the CD. In order to achieve this recording density, the track pitch is reduced to 0.74 xcexcm and the track recording density (number of data on the track per a unit length) is increased. With the increase in the recording density, the wavelength of the light beam is reduced to 650 nm. In order to reliably reproduce information recorded in the disk even when the disk is inclined, the thickness of a base substrate of the disk is 0.6 mm, that is, thinner than that of the CD. The diameter of the DVD is approximately equal to that of the CD. Hereinafter, this DVD is called a single-layer DVD.
Besides the single-layer DVD mentioned above, there is also a double-layer DVD as shown in FIG. 26. In FIG. 26, reference numeral 4 designates a first layer, numeral 5 designates a second layer, numeral 6 designates an intermediate layer, and numeral 10 designates a base substrate of the DVD. The DVD is irradiated with a light beam at the rear surface of the base substrate 10. Like the single-layer DVD, the first layer 4 wherein information is recorded is 0.6 mm distant from the rear surface of the base substrate 10. A reflecting film comprising Au or the like is employed as the first layer 4, and the reflectivity is reduced to about 35%. So, a part of the light beam passes through the first layer 4. This first layer serves as a first information surface. The second layer 5 is located on the first layer 4 with the 40 xcexcm thick intermediate layer 6 between them. The light beam passing through the first layer 4 is reflected by the second layer 5 and travels through the intermediate layer 6, the first layer 4, and the base substrate 10. This second layer serves as a second information surface. Thereby, information recorded in the first layer 4 and the second layer 5 can be reproduced. The second layer 5 comprises aluminum or the like, and the reflectivity is about 90%. The recording capacity of this double-layer DVD is about twice as large as that of the single-layer DVD. In this double-layer DVD, when information recorded in the first information surface 4 is reproduced, focusing is performed on the first information surface 4. When information recorded in the second information surface 5 is reproduced, after the focal point is moved from the first information surface 4 to the second information surface 5, focusing is performed on the second information surface 5.
When a CD and a DVD are reproduced using an optical disk apparatus, the apparatus is provided with an optical system for reproducing the CD and an optical system for reproducing the DVD because the CD and the DVD have different base material thicknesses, and the optical systems are switched according to a disk set in the apparatus. In order to identify whether the disk set in the apparatus is a CD or a DVD, a cartridge containing the disk has a hole for discrimination.
However, when the disk is not contained in a cartridge, it is impossible to identify the disk using a cartridge. If the optical system for the DVD is used for the CD, information is not correctly reproduced because of the difference in base material thicknesses between the CD and the DVD.
Meanwhile, there is a disk called CD-R which is a recordable optical disk of write once read many type. When the CD-R, which employs the same optical system for the CD, is set in the optical disk apparatus, if the optical system for the DVD is selected by mistake, information recorded in the CD-R is sometimes destroyed. This destruction is attributed to the fact that the CD-R usually employs, for a recording film, an organic coloring material that highly absorbs light having a wavelength of 650 nm and, therefore, the recording film is easily destroyed.
An object of the present invention is to provide an optical disk apparatus that can discriminate between a CD and a DVD even when these disks are not contained in cartridges.
Another object of the present invention is to provide an optical disk apparatus that can discriminate between a CD-R and a DVD without destroying an information surface of the CD-R when the CD-R is set in the apparatus by mistake.
Other objects and advantages of the invention will become apparent from the detailed description that follows. The detailed description and specific embodiments described are provided only for illustration since various modifications within the scope of the invention will be apparent to those of skill in the art from the detailed description.
According to a first aspect of the present invention, there is provided an optical disk apparatus comprising means for moving a focal point of a light beam for reproducing information recorded on an information face of a disk, in the direction perpendicular to the information face; means for detecting a reflected light from the disk; and means for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate. In this apparatus, a maximum value AS1Lmax of an output signal from the reflected light detecting means and a maximum value ENVmax of an amplitude of an information reproducing signal are detected while driving the focal point moving means so that the focal point passes through the information face, and the discriminating means discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of the ratio of ENVmax to AS1Lmax. Therefore, it is possible to discriminate between a DVD having a thin base substrate and a CD having a thick base substrate.
According to a second aspect of the present invention, there is provided an optical disk apparatus comprising means for moving a focal point of a light beam for reproducing information recorded on an information face of a disk, in the direction perpendicular to the information face; means for detecting a reflected light from the disk; a signal detecting means for detecting a prescribed frequency component from an output signal from the reflected light detecting means; and means for discriminating whether the disk set in the apparatus is a disk having a high track recording density or a disk having a low track recording density. In this apparatus, the discriminating means discriminates whether the disk set in the apparatus is a disk having a high track recording density or a disk having a low track recording density on the basis of an output signal from the signal detecting means when the focal point moving means is driven so that the focal point passes through the information face. Therefore, it is possible to discriminate between a disk having a high tract recording density and a disk having a low track recording density.
According to a third aspect of the present invention, there is provided an optical disk apparatus comprising means for moving a focal point of a light beam for reproducing information recorded on an information face of a disk, in the direction perpendicular to the information face; means for detecting a reflected light from the disk; means for digitizing an output signal from the reflected light detecting means; means for measuring a high level period or a low level period of time for an output signal from the digitizing means; and means for discriminating whether the disk set in the apparatus is a disk having a high track recording density or a disk having a low track recording density. In this apparatus, the discriminating means discriminates whether the disk set in the apparatus is a disk having a high track recording density or a disk having a low track recording density on the basis of a signal output from the period measuring means when the focal point moving means is driven so that the focal point passes through the information face. Therefore, it is possible to discriminate between a disk having a high track recording density and a disk having a low track recording density.
According to a fourth aspect of the present invention, there is provided an optical disk apparatus comprising means for moving a focal point of a light beam for reproducing information recorded on an information face of a disk, in the direction perpendicular to the information face; means for detecting a reflected light from the disk; and means for discriminating the disk set in the apparatus as a disk employing an organic coloring material for a recording film when a signal output from the reflected light detecting means when the focal point moving means is driven so that the focal point passes through the information face is lower than a prescribed level. Therefore, it is possible to discriminate a CD-R in a relatively simple structure.
According to a fifth aspect of the present invention, the above-mentioned apparatus further comprises a focus error signal detector detecting a focus error signal that shows a focused state of the light beam irradiating the information face of the disk on the basis of the output signal from the reflected light detecting means, and the discriminating means discriminates the disk set in the apparatus as a disk employing an organic coloring material for a recording film when an amplitude of the focus error signal is lower than a prescribed level. Therefore, it is possible to discriminate a CD-R in a relatively simple structure.
According to a sixth aspect of the present invention, in the above-mentioned apparatus, the discrimination of the disk employing an organic coloring material is performed with a light beam having an intensity lower than the intensity of the light beam for reproducing the information. Therefore, even when the disk set in the apparatus is a CDR, information recorded in the CD-R is not destroyed when the disk is discriminated.
According to a seventh aspect of the present invention, there is provided an optical disk apparatus comprising means for moving a focal point of a light beam for reproducing information recorded on an information face of a disk, in the direction perpendicular to the information face; means for detecting a reflected light from the disk; and means for discriminating whether the disk set in the apparatus is a disk having one information face or a disk having two information faces. In this apparatus, the discriminating means discriminates the disk set in the apparatus as a disk having two information faces when a signal output from the reflected light detecting means when the focal point moving means is driven so that the focal point passes through the information face is lower than a prescribed level. Therefore, the discrimination between a single-layer DVD and a double-layer DVD can be performed using the maximum value of the ENV signal, in a relatively simple structure.
According to an eighth aspect of the present invention, the above-mentioned apparatus further comprises a focus error signal detector detecting a focus error signal that shows a focused state of the light beam irradiating the information face of the disk on the basis of an output signal from the reflected light detecting means, and the discriminating means discriminates the disk set in the apparatus as a disk having two information faces when an amplitude of the focus error signal is lower than a prescribed level. Therefore, it is possible to discriminate between a single-layer DVD and a double-layer DVD.
According to a ninth aspect of the present invention, there is provided an optical disk apparatus comprising means for moving a focal point of a light beam for reproducing information recorded on an information face of a disk, in the direction perpendicular to the information face; means for detecting a reflected light from the disk; and means for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of a maximum value of an amplitude of an information reproducing signal output from the reflected light detecting means when the focal point moving means is driven so that the focal point passes through the information face. Therefore, the discrimination between a DVD having a thin base substrate and a CD having a thick base substrate can be performed in a relatively simple structure.
According to a tenth aspect of the present invention, in the above-mentioned apparatus, the information recorded in the disk is reproduced using an optical system for a disk having a thin base substrate. Therefore, when a disk having a thin base substrate is set in the apparatus, the time interval before the reproduction of information is reduced.
According to an eleventh aspect of the present invention, in the above-mentioned apparatus, the moving speed of the focal point is reduced by controlling the focal point moving means when the output from the reflected light detecting means exceeds a prescribed level. Therefore, level changes of an ASiL signal, an ENV signal, and an FE signal become gentle, and maximum values of amplitudes of these signals are accurately detected, whereby the reliability of the disk discrimination is improved.
According to a twelfth aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, the apparatus comprising means for moving the first and second focal points in the direction perpendicular to the information face; means for detecting a reflected light from the disk; a focus error detecting means for detecting a focused state of a light beam irradiating the information face, on the basis of an output signal from the reflected light detecting means; means for controlling focusing so that the focused state of the light beam becomes a desired state, on the basis of an output signal from the focus error detecting means; and means for generating a timing signal for driving the focusing control means on the basis of an output signal from the focus error detecting means. In this apparatus, the focal point moving means is driven so that the focal points go away from the disk, and the focusing control means is operated in response to the timing signal. When no information is reproduced, the focusing control means is immobilized, and the focal point moving means is driven so that the focal points approach the disk, and the focusing control means is operated in response to the timing signal. Therefore, even though the apparatus is not provided with a disk discriminating means, the focusing control can be performed with focal points suitable for the disk having a thick base substrate and the disk having a thin base substrate, respectively. In addition, when a disk having a thin base substrate is set in the apparatus, the rise time of the apparatus can be reduced.
According to a thirteenth aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, the apparatus comprising means for moving the first and second focal points in the direction perpendicular to the information face; means for detecting a reflected light from the disk; a focus error detecting means for detecting a focused state of a light beam irradiating the information face on the basis of an output signal from the reflected light detecting means; means for controlling focusing so that the focused state of the light beam becomes a desired state on the basis of an output signal from the focus error detecting means; and means for generating a timing signal for driving the focusing control means on the basis of an output signal from the focus error detecting means. In this apparatus, the focal point moving means is driven so that the focal points approach the disk, and the focusing control means is operated in response to the timing signal. When no information is reproduced, the focusing control means is immobilized, and the focal point moving means is driven so that the focal points go away from the disk, and the focusing control means. is operated in response to the timing signal. Therefore, even though the apparatus is not provided with a disk discriminating means, focusing control can be performed with focal points suitable for the disk having a thick base substrate and the disk having a thin base substrate, respectively. In addition, when a disk having a thick base substrate is set in the apparatus, the rise time of the apparatus can be reduced.
According to a fourteenth aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, this apparatus comprising means for moving the first and second focal points in the direction perpendicular to the information face; means for detecting a reflected light from the disk; a focus error detecting means for detecting a focused state of a light beam irradiating the information face on the basis of an output signal from the reflected light detecting means; means for controlling focusing so that the focused state of the light beam becomes a desired state on the basis of an output signal from the focus error detecting means; means for generating a timing signal for driving the focusing control means on the basis of an output signal from the focus error detecting means; and means for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate. In this apparatus, when the disk set in the apparatus is discriminated as a disk having a thick base substrate, the focal point moving means is driven so that the focal points approach the disk, and the focusing control means is operated in response to the timing signal. Therefore, when a disk having a thick base substrate is set in the apparatus, the focusing control can be performed with a focal point suitable for the disk, and the rise time of the apparatus can be reduced.
According to a fifteenth aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, the apparatus comprising means for moving the first and second focal points in the direction perpendicular to the information face; means for detecting a reflected light from the disk; a focus error detecting means for detecting a focused state of a light beam irradiating the information face on the basis of an output signal from the reflected light detecting means; means for controlling focusing so that the focused state of the light beam becomes a desired state on the basis of an output signal from the focus error detecting means; means for generating a timing signal for driving the focusing control means on the basis of an output signal from the focus error detecting means; and means for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate. When the disk set in the apparatus is discriminated as a disk having a thin base substrate, the focal point moving means is driven so that the focal points go away from the disk, and the focusing control means is operated in response to the timing signal. Therefore, when a disk having a thin base substrate is set in the apparatus, the focusing control can be performed with a focal point suitable for the disk, and the rise time of the apparatus can be reduced.
According to a sixteenth aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, the apparatus comprising means from moving the first and second focal points in the direction perpendicular to the information face; means for detecting a reflected light from the disk; a focus error detecting means for detecting a focused state of a light beam irradiating the information face, on the basis of an output signal from the reflected light detecting means; means for controlling focusing so that the focused state of the light beam becomes a desired state on the basis of an output signal from the focus error detecting means; means for generating a timing signal for driving the focusing control means on the basis of an output signal from the focus error detecting means; and means for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate. When the disk set in the apparatus is discriminated as a disk having a thick base substrate, the focal point moving means is driven so that the focal points approach the disk, and the focusing control means is operated in response to the timing signal. When the disk set in the apparatus is discriminated as a disk having a thin base substrate, the focal point moving means is driven so that the focal points go away from the disk, and the focusing control means is operated in response to the timing signal. Therefore, the focusing control can be performed with focal points suitable for the disk having a thick base substrate and the disk having a thin base substrate, respectively. In addition, the rise time of the apparatus can be reduced in both cases where a disk having a thick base substrate is set and where a disk having a thin base substrate is set.
According to a seventeenth aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, the apparatus comprising means for moving the first and second focal points in the direction perpendicular to the information face; means for detecting a reflected light from the disk, having a first light responsive region that receives a center portion of the reflected light and a second light responsive region that receives a peripheral portion of the reflected light; and means for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate, on the basis of signals detected by the first and second light responsive regions when the focal point moving means is driven so that the first and second focal points pass through the information face. Therefore, the discrimination between a disk having a thick base substrate and a disk having a thin base substrate can be performed.
According to an eighteenth aspect of the present invention, in the above-mentioned apparatus, the discriminating means detects that a focal point of a light beam suitable for the disk is near the information face from the level of an information reproducing signal detected by the reflected light detecting means, and then discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of the signals detected by the first and second light responsive regions. Therefore, the discrimination of the disk set in the apparatus is accurately performed.
According to an nineteenth aspect of the present invention, in the above-mentioned apparatus, the discriminating means detects that a focal point of a light beam suitable for the disk is near the information face on the basis of the ratio of a low frequency signal level of the output signal from the reflected light detecting means to the information reproducing signal level. Therefore, the discrimination of the disk can be performed accurately even when the reflectivity of the disk varies.
According to a twentieth aspect of the present invention, in the above-mentioned apparatus, the discriminating means comprises means for dividing an amplitude of an information reproducing signal by a low frequency signal level of an output signal from the reflected light detecting means; and means for measuring an amount of light AS1Lp received by the first light responsive region, an amount of light AS2Lp received by the second light responsive region, and an amplitude ENVp of the information reproducing signal when a value obtained by the division attains a maximum value while driving the focal point moving means so that the first and second focal points pass through the information face. The discriminating means discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of the ratio of AS1Lpxc3x97ENVp to AS2Lp. Therefore, the precision in the discrimination of the disk is improved.
According to a twenty-first aspect of the present invention, in the above-mentioned apparatus, the discriminating means comprises means for adding an output signal from the first light responsive region to an output signal from the second light responsive region; means for dividing an amplitude of an information reproducing signal by a low frequency signal level of an output signal from the reflected light detecting means; and means for measuring a maximum value ASLmax obtained by the adding means and measuring an amount of light AS1Lp received by the first light responsive region, an amount of light AS2Lp received by the second light responsive region, and an amplitude ENVp of the information reproducing signal when a value obtained by the dividing means attains a maximum value while driving the focal point moving means so that the first and second focal points pass through the information face. The discriminating means discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of the ratio of AS1Lpxc3x97ENVp to AS2Lpxc3x97ASLmax. Therefore, the discrimination of the disk can be performed accurately even when the reflectivity of the disk varies.
According to a twenty-second aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, the apparatus comprising means for moving the first and second focal points in the direction perpendicular to the information face; first and second light detecting means for detecting a reflected light from the disk, the second light detecting means receiving a larger portion of the reflected light than the first light detecting means; and means for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a think base substrate on the basis of signals detected by the first and second light detecting means when the focal point moving means is driven so that the first and second focal points pass through the information face. Therefore, the discrimination between a disk having a thick base substrate and a disk having a thin base substrate can be performed.
According to a twenty-third aspect of the present invention, in the above-mentioned apparatus, the discriminating means detects that a focal point of a light beam suitable for the disk is near the information face from the level of information reproducing signals detected by the first and second light detecting means, and then discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of signals detected by the first and second light receiving means. Therefore, the discrimination of the disk can be performed accurately.
According to a twenty-fourth aspect of the present invention, in the above-mentioned apparatus, the discriminating means detects that a focal point of a light beam suitable for the disk is near the information face on the basis of the ratio of a low frequency signal level in the output signals from the first and second light detecting means to the information reproducing signal level. Therefore, the discrimination of the disk can be performed accurately even when the reflectivity of the disk varies.
According to a twenty-fifth aspect of the present invention, in the above-mentioned apparatus, the discriminating means comprises means for dividing an amplitude of an information reproducing signal by a low frequency signal level of output signals from the first and second light detecting means; and means for measuring an amount of light AS1Lp received by the first light detecting means, an amount of light AS2Lp received by the second light detecting means, and an amplitude ENVp of the information reproducing signal when a value obtained by the division attains a maximum value while driving the focal point moving means so that the first and second focal points pass through the information face. The discriminating means discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of the ratio of AS1Lpxc3x97ENVp to AS2Lp. Therefore, the precision in the discrimination of the disk is improved.
According to a twenty-sixth aspect of the present invention, in the above-mentioned apparatus, the discriminating means comprises means for adding an output signal from the first light detecting means to an output signal from the second light detecting means; means for dividing an amplitude of an information reproducing signal by a low frequency signal level of output signals from the first and second light detecting means; and means for measuring a maximum value ASLmax obtained by the adding means and measuring an amount of light AS1Lp received by the first light detecting means, an amount of light AS2Lp received by the second light detecting means, and an amplitude ENVp of the information reproducing signal when a value obtained by the dividing means attains a maximum value while driving the focal point moving means so that the first and second focal points pass through the information face. The discriminating means discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of the ratio of AS1Lpxc3x97ENVp to AS2Lpxc3x97ASLmax. Therefore, the discrimination of the disk can be performed accurately even when the reflectivity of the disk varies.
According to a twenty-seventh aspect of the present invention, there is provided an optical disk apparatus for reproducing both a disk having one information face and a disk having two information faces by irradiating the disk with a focused light beam, the apparatus comprising means for moving a focal point of the light beam in the direction perpendicular to the information face; means for detecting a reflected light from the disk, having a first light responsive region that receives a center portion of the reflected light and a second light responsive region that receives a peripheral portion of the reflected light; and means for discriminating whether the disk set in the apparatus is a disk having one information face or a disk having two information faces on the basis of signals detected by the first and second light responsive regions when the focal point moving means is driven so that the focal point passes through the information face. Therefore, the discrimination between a disk having one information face and a disk having two information faces can be performed.
According to a twenty-eighth aspect of the present invention, in the above-mentioned apparatus, the discriminating means detects that the focal point of the light beam is near the information face from the level of an information reproducing signal detected by the reflected light detecting means, and then discriminates whether the disk set in the apparatus is a disk having one information face or a disk having two information faces on the basis of the signals detected by the first and second light responsive regions. Therefore, the discrimination of the disk can be performed accurately.
According to a twenty-ninth aspect of the present invention, in the above-mentioned apparatus, the discriminating means detects that the focal point of the light-beam is near the information face on the basis of the ratio of a low frequency signal level of the output signal from the reflected light detecting means to the information reproducing signal level. Therefore, the discrimination of the disk can be performed accurately even when the reflectivity of the disk varies.
According to a thirtieth aspect of the present invention, in the above-mentioned apparatus, the discriminating means comprises means for dividing an amplitude of an information reproducing signal by a low frequency signal level of an output signal from the reflected light detecting means; and means for measuring an amount of light AS1Lp received by the first light responsive region, an amount of light AS2Lp received by the second light responsive region, and an amplitude ENVp of the information reproducing signal when a value obtained by the division attains a maximum value while driving the focal point moving means so that the focal point passes through the information face. The discriminating means discriminates whether the disk set in the apparatus is a disk having one information face or a disk having two information faces on the basis of the ratio of AS1Lpxc3x97ENVp to AS2Lp. Therefore, the precision in the discrimination of the disk is improved.
According to a thirty-first aspect of the present invention, in the above-mentioned apparatus, the discriminating means comprises means for adding an output signal from the first light responsive region to an output signal from the second light responsive region; means for dividing an amplitude of an information reproducing signal by a low frequency signal level of an output signal from the reflected light detecting means; and means for measuring a maximum value ASLmax obtained by the adding means and measuring an amount of light AS1Lp received by the first light responsive region, an amount of light AS2Lp received by the second light responsive region, and an amplitude ENVp of the information reproducing signal when a value obtained by the dividing means attains a maximum value while driving the focal point moving means so that the focal point passes through the information face. The discriminating means discriminates whether the disk set in the apparatus is a disk having one information face or a disk having two information faces on the basis of the ratio of AS1Lpxc3x97ENVp to AS2Lpxc3x97ASLmax. Therefore, the discrimination of the disk can be performed accurately even when the reflectivity of the disk varies.
According to a thirty-second aspect of the present invention there is provided an optical disk apparatus for reproducing both a disk having one information face and a disk having two information faces by irradiating the disk with a focused light beam, the apparatus comprising means for moving a focal point in the direction perpendicular to the information face; first and second light detecting means for detecting a reflected light from the disk, the second light detecting means receiving a larger portion of the reflected light than the first light detecting means; and means for discriminating whether the disk set in the apparatus is a disk having one information face or a disk having two information faces on the basis of signals detected by the first and second light detecting means when the focal point moving means is driven so that the focal point passes through the information face. Therefore, the discrimination between a disk having one information face and a disk having two information faces can be performed.
According to a thirty-third aspect of the present invention, in the above-mentioned apparatus, the discriminating means detects that the focal point of the light beam is near the information face, from the level of information reproducing signals detected by the first and second light detecting means, and then discriminates whether the disk set in the apparatus is a disk having one information face or a disk having two information faces on the basis of signals detected by the first and second light receiving means. Therefore, the discrimination of the disk can be performed accurately.
According to a thirty-fourth aspect of the present invention, in the above-mentioned apparatus, the discriminating means detects that the focal point of the light beam is near the information face on the basis of the ratio of a low frequency signal level in the output signals from the first and second light detecting means to the information reproducing signal level. Therefore, the discrimination of the disk can be performed accurately even when the reflectivity of the disk varies.
According to a thirty-fifth aspect of the present invention, in the above-mentioned apparatus, the discriminating means comprises means for dividing an amplitude of an information reproducing signal by a low frequency signal level of output signals from the first and second light detecting means; and means for measuring an amount of light AS1Lp received by the first light detecting means, an amount of light AS2Lp received by the second light detecting means, and an amplitude ENVp of the information reproducing signal when a value obtained by the division attains a maximum value while driving the focal point moving means so that the focal point passes through the information face. The discriminating means discriminates whether the disk set in the apparatus is a disk having one information face or a disk having two information faces on the basis of the ratio of AS2Lpxc3x97ENVp to AS2Lp. Therefore, the precision in the discrimination of the disk can be improved.
According to a thirty-sixth aspect of the present invention, in the above-mentioned apparatus, the discriminating means comprises means for adding an output signal from the first light detecting means to an output signal from the second light detecting means; means for dividing an amplitude of an information reproducing signal by a low frequency signal level of output signals from the first and second light detecting means; and means for measuring a maximum value ASLmax obtained by the adding means and measuring an amount of light ASILp received by the first light detecting means, an amount of light AS2Lp received by the second light detecting means, and an amplitude ENVp of the information reproducing signal when a value obtained by the dividing means attains a maximum value while driving the focal point moving means so that the focal point passes through the information face. The discriminating means discriminates whether the disk set in the apparatus is a disk having one information face or a disk having two information faces on the basis of the ratio of AS1Lpxc3x97ENVp to AS2Lpxc3x97ASLmax. Therefore, the discrimination of the disk can be performed accurately even when the reflectivity of the disk varies.
According to a thirty-seventh aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, the apparatus comprising means for moving the first and second focal points in the direction perpendicular to the information face; means for detecting a reflected light from the disk; means for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate; and an information face detecting means for detecting that a focal point of a light beam suitable for the disk is near the information face, from an output signal of the reflected light detecting means, while driving the focal point moving means so that the first and second focal points pass through the information face. In this apparatus, the discriminating means discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of the ratio of a maximum value ASLmax of a signal output from the reflected light detecting means to a level ASLp of a signal output from the reflected light detecting means when the information face is detected by the information face detecting means, while driving the focal point moving means so that the first and second focal points pass through the information face. Therefore, the discrimination between a disk having a thick base substrate and a disk having a thin base substrate can be performed.
According to a thirty-eighth aspect of the present invention, in the above-mentioned apparatus, the information face detecting means detects that a focal point of a light beam suitable for the disk is near the information face on the basis of the ratio of a low frequency signal level of an output signal from the reflected light detecting means to an information reproducing signal level of the output signal. Therefore, the discrimination of the disk can be performed accurately even when the reflectivity of the disk varies.
According to a thirty-ninth aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, the apparatus comprising means for moving the first and second focal points in the direction perpendicular to the information face; means for detecting a reflected light from the disk; and means for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate. In this apparatus, a maximum value AS1Lmax of an output from the reflected light detecting means and a maximum value ENVmax of an amplitude of an information reproducing signal are measured while driving the focal point moving means so that the first and second focal points pass through the information face, and the discriminating means discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate on the basis of the ratio of ENVmax to AS1Lmax. Therefore, the discrimination between a disk having a thick base substrate and a disk having a thin base substrate can be performed.
According to a fortieth aspect of the present invention, there is provided an optical disk apparatus for reproducing information recorded on an information face of a disk using an optical head having a first focal point for reproducing a disk having a thick base substrate and a second focal point for reproducing a disk having a thin base substrate, the apparatus comprising means for moving the first and second focal points in the direction perpendicular to the information face; means for detecting a reflected light from the disk; a focus error detecting means for detecting focused state of a light beam irradiating the information face on the basis of an output signal from the reflected light detecting means; means for controlling focusing so that the focused state of the light beam becomes a desired state on the basis of an output signal from the focus error detecting means, the focusing control means including an amplifier having a variable amplification factor and amplifying the output signal from the focus error detecting means; and an information face detecting means for detecting that a focal point of a light beam suitable for the disk is near the information face, from an output signal of the reflected light detecting means. In this apparatus, the amplification factor of the amplifier is set on the basis of an output value from the reflected light detecting means when the information face detecting means outputs an information face detecting signal, while driving the focal point moving means so that the first and second focal points pass through the information face. Therefore, even when the reflectivity of the disk varies, the amplitude of the FE signal is constant, whereby an accurate timing for performing the focusing control is obtained.
According to a forty-first aspect of the present invention, in the above-mentioned apparatus, after setting the amplification factor of the amplifier, the focusing control means is operated by detecting that an output signal from the amplifier reaches a prescribed value. Therefore, the focusing control is avoided from being performed at a wrong timing due to noise or the like.
According to a forty-second aspect of the present invention, in the above-mentioned apparatus, the information face detecting means detects that a focal point of a light beam suitable for the disk is near the information face on the basis of the ratio of a low frequency signal level of an output signal from the reflected light detecting means to an information reproducing signal level of the output signal. Therefore, even when the reflectivity of the disk varies, the presence of the suitable focal point in the vicinity of the information face can be detected at an accurate timing.
According to a forty-third aspect of the present invention, in the above-mentioned apparatus, the discrimination of the disk set in the apparatus is performed after the focal point passes through the information face twice. Therefore, the detection of the reflected light is accurately performed, whereby the precision in the discrimination of the disk is improved.
According to a forty-fourth aspect of the present invention, in the above-mentioned apparatus, the focal point is slightly moved in the direction perpendicular to a track on the disk during a period of time when the focal point is passed through the information face by controlling the focusing control means. Therefore, it is avoided that the focal point is always positioned between tracks, whereby the precision in the discrimination of the disk is improved.
According to a forty-fifth aspect of the present invention, in the above-mentioned apparatus, the moving speed of the focal point is reduced by controlling the focal point moving means when an output value from the reflected light detecting means exceeds a prescribed value. Therefore, the change of the reflected light amount becomes gentle, and the signal level is accurately detected, whereby the precision in the discrimination of the disk is improved.